<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        const p = new Promise(function(resolve, reject) { //异步成功调用resolve ，失败调用reject
            setTimeout(function() {
                // let data = '数据库中的用户数据';
                // resolve(data);
                let error = '数据读取失败';
                reject(error);
            }, 1000)
        })

        //调用promise对象的then方法
        //函数中异步成功则调用第一个函数value，失败则调用韩式reason
        p.then(function(value) {
            console.log(value);
        }, function(reason) {
            console.error(reason);
        })
    </script>
</body>

</html>